DOVER — Even though it’s still early in the Division II season, the Dover High School boys hockey team knew how big Wednesday night’s game against rival Oyster River was going to be.

With the Bobcats and Green Wave both expected to contend for a high seed in the tournament, Dover’s 3-1 win at Dover Arena set the stage for what could be a lengthy struggle for a home playoff game come late February.

“It was pretty big,” Dover coach Steve Riker said. “There are five or six teams in the division that will kind of be up there. We’re all going to be fighting for spots there, so tonight was big to be able to beat them and get two points on them.”

Dover sophomore forward Mitchell Welch scored his team-leading fifth and sixth goals of the season on Wednesday, including the eventual game winner in the second period.

“He’s a very skilled kid and we’ve given him more ice time this year,” Riker said about Welch. “He’s taken advantage of it.”

The Green Wave improved to 3-0 while Oyster River fell to 2-1. Bobcats coach Griff Richard agreed that the game loomed large, especially since Dover is one of only three clubs his crew will have to meet twice this season. The rematch is scheduled for Feb. 21 at the Whittemore Center.

“Our strength of schedule is probably the hardest, if not one of the hardest,” Richard said. “You can’t give away a game. We didn’t give this game away tonight. I thought we fought, but we’re still young on defense.”

After a scoreless first period, Welch put Dover on the board just 1:40 into the middle frame. A scrum in front of the net resulted in a shot by Dover’s Cam Crowley from high in the slot. Oyster River goalie Brennan Young made the initial save with his pads, but Welch swept in the rebound through the five-hole for the 1-0 lead.

“It was just laying there in front of his pads and I just hit it in,” Welch said.

Oyster River missed out on a few opportunities to even the score. The Bobcats were about to go on a power play that was negated when Patrick McDonough was called for a hit after the whistle, negating the advantage. Later, the Bobcats’ Connor McDonough and Julien Pelletier were called for penalties 41 seconds apart, giving Dover a 5-on-3 for 1:19, which they did not convert.

“We’ve been relying on our skill, hopefully, to carry us a little bit,” Richard said. “I think we were panicking with the puck on the power play, not getting set up, which is a high-school hockey thing. We rush to get it to the net.”

Dover had trouble staying out the box as well, especially senior forward Eli Cobb, who was thrice sent to the box in the middle frame. On the third penalty, the Bobcats made Dover pay when Trevar Delisle sent a shot from the blue line past Dover goalie Luc Ravenelle for the equalizer at 13:47. That’s where it stood after two stops.

“We had some good chances on our power plays,” Riker said. “Their goalie made some pretty good saves.”

Welch scored the game-winner in the final stanza when he sent in a rebound following a scramble in front of the net for a 2-1 lead at 7:53. Any hope the Bobcats had of tying the game again took a hit when Griffin Sperry was called for tripping at 10:22, giving Dover a power play.

Young was pulled with just over a minute left, and Dover’s Sam Bovee buried an empty-netter at 14:29. Young made 29 saves and Ravenelle made 24.

“We didn’t have the offense or the defense tonight,” said Patrick McDonough, who assisted on Delisle’s goal. “We didn’t come out hard. This was our first big test this season, and it showed us that we can’t just roll through teams.”

The Bobcats had beaten their first two opponents by a combined score of 14-4.

Both teams play their last regular-season game of 2012 on Saturday. Oyster River hosts Merrimack and Dover hosts Bow, another team expected to contend for a deep tournament run.